Any research findings of science, arts, medicine, literature or technology related are published in research journals or publications.
There are thousands of journals available for publications.
Hence they are given an impact factor as an indicative of its quality and value.
It is one of the ranking or quality criteria for scientific journals.
The more the I.F. the better is the journal and many scientists and academicians compete to get their findings to publish there.
The impact factor is mentioned in terms of mathematical number as 0, 1, 2, 3, 4 till as per knowledge 55. Further they may have sub digits as 0.5 or 1.2 or 2.5 as impact factor.
The overall impact factor for a journal is best considered over a five year period as impact factors vary for journals on yearly basis.
This variation depends on factors like number of citation of any research from the said journal, even number of issues per year etc.
For a researcher or academicians involved in research, the performance is measured based on factors like number of research publications, the impact factor of the publications, the H-factor also called as citation factors, number of students got their degrees under him/her, number of patents possessed and also number of projects successfully completed.
These above factors help them in qualifying for a higher post or position in the field of research.
So impact factor of journal seems to be very important for them. For instance, during an interview if two researchers have 10 papers each published in quality journals. And if all other above factors have equal stand in between the two, then impact factors are taken into account for grading. On addition of these impact factors those with higher value is preferred than the other.
So to withstand the competition, the researcher tries to get his study and findings published in a journal of higher impact factor. This impact factor seems to be an ego satisfying factor even for the scientists.
On the other hand the editors and reviewers of journals receive many findings to be published from researchers. These editors and reviewers screen the topics with an aim to select better study and finding for publication and reject the low standard ones. In doing so the editors try to keep up their journal impact factor and even enhance it year by year.
There are journal whose impact might be zero presently and in a span of two year it might shoot up to 3 or even 5 directly and on the other hand there are journal with good impact factor like 4 which drop themselves to 2.5 or so. So editors and reviewers have hard task in maintaining the impact factors.